1. Field of the Invention
The invention relates to an optical device and an illumination apparatus, and more particularly to a light guide plate and an illumination apparatus using the light guide plate.
2. Description of Related Art
Conventionally, the light source of the illuminations and the advertisement light boxes are fluorescent lamp tubes, cold cathode fluorescence lamps (CCFLs), and light emitting diodes (LEDs). When the fluorescent lamp tubes or the cold cathode fluorescence lamps are used as the illumination light source, the application products possess the disadvantages of large weight, short lifetime, and low space utilization due to the limitation of the lifetime and the dimension of the light source itself. Besides, since there is trace mercury vapor or solid state mercury within the lamp tube, when the lamps are thrown away or repaired, it is necessary to recycle the lamp tubes to prevent the environment from being polluted.
Accordingly, in the public place, the light emitting diodes are gradually used as the light sources in the advertisement light boxes, the exhibition lamps or bill lamps. The methods for emitting light beams of the light boxes may be generally categorized into the single-sided illumination and two-sided illumination. Typically, the light box with the two-sided illumination includes one or more light emitting diode lamp and two light guide plates. Between the two light guide plates, there is a reflection plate. The aforementioned light box with the two-sided illumination utilizes that the light source laterally emits light beam onto the upper-side light guide plate and the lower-side light guide plate so that the light beam is uniformly transmitted from the upper surface and the lower surface of the light box. Moreover, the net points may be printed on the upper surface and the lower surface of the light guide plate so that the light beam within the light guide plate may be uniformly transmitted from the upper surface and the lower surface of the light guide plate. However, the aforementioned two methods possess the disadvantages. The former method leads to the increasing of the weight and the thickness of the lamp, and the later method leads to the problem of poor brightness.
Taiwan Patent Nos. M298750 and M254682 each disclose an advertisement billboard with the two-sided illumination using two cold cathode fluorescent lamps as the light sources. Taiwan Patent Nos. M341284 and M2777075 each disclose a light box with the two-sided illumination using two light guide plates to achieve the two-sided illumination effect. Moreover, Taiwan Patent Nos. M348297 and M275432 each disclose an advertisement light box. In Taiwan Patent No. M275432, there are micro-structures disposed on the illumination surface.
Also, Taiwan Patent No. M348296 discloses an advertisement light box with various optical films. Moreover, Taiwan Patent Nos. I259312, I244566, I303006, and M287951 disclose backlight modules or displays with the two-sided illuminations.